# -*- coding: utf-8 -*-

# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html

from scrapy import signals
import json ##处理json的包
import redis #Python操作redis的包
import random #随机选择
from csdn.useragent import agents #导入useragent
from csdn.cookies import init_cookie,get_cookie # 导入cookies
from scrapy.downloadermiddlewares.useragent import UserAgentMiddleware #UserAegent中间件
from scrapy.downloadermiddlewares.retry import RetryMiddleware #重试中间件
import logging

logger = logging.getLogger(__name__)

class CsdnSpiderMiddleware(object):
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the spider middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, dict or Item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Request, dict
        # or Item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)


class CsdnDownloaderMiddleware(object):
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        # Called for each request that goes through the downloader
        # middleware.

        # Must either:
        # - return None: continue processing this request
        # - or return a Response object
        # - or return a Request object
        # - or raise IgnoreRequest: process_exception() methods of
        #   installed downloader middleware will be called
        return None

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest
        return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)

# 随机UserAgent
class UserAgentmiddleware(UserAgentMiddleware):

    def process_request(self, request, spider):
        agent = random.choice(agents)
        request.headers["User-Agent"] = agent


class CookieMiddleware(RetryMiddleware):

    def __init__(self, settings, crawler):
        RetryMiddleware.__init__(self, settings)
        self.rconn = redis.from_url(settings['REDIS_URL'], db=9, decode_responses=True)  ##decode_responses设置取出的编码为str

        init_cookie(self.rconn, crawler.spider.name)

    @classmethod
    def from_crawler(cls, crawler):
        return cls(crawler.settings, crawler)

    def process_request(self, request, spider):
        redisKeys = self.rconn.keys()
        while len(redisKeys) > 0:
            elem = random.choice(redisKeys)
            if spider.name + ':Cookies' in elem:
                cookie = json.loads(self.rconn.get(elem))
                request.cookies = cookie
                request.meta["accountText"] = elem.split("Cookies:")[-1]
                break